Method and apparatus for wide-band imaging based on narrow-band image data

ABSTRACT

In one embodiment, an imaging method may include receiving an intensity value of a first spectral channel associated with a pixel location. The intensity value of the first spectral channel may be based on electromagnetic radiation reflected from an object after being emitted from a narrow-band electromagnetic radiation source. The method may further include defining an intensity value of a second spectral channel based on the intensity value of the first spectral channel. The second spectral channel may be associated with a spectral region of electromagnetic radiation different from a spectral region of electromagnetic radiation associated with the first spectral channel. The method may also include associating the intensity value of the second spectral channel with the pixel location.

CROSS REFERENCE TO RELATED APPLICATION

This patent application is a continuation of U.S. patent applicationSer. No. 14/021,476, filed Sep. 9, 2013, now U.S. Pat. No. 9,319,601,which is a continuation of U.S. patent application Ser. No. 12/873,643,filed Sep. 1, 2010, now U.S. Pat. No. 8,553,975, which claims thebenefit of priority of U.S. Provisional Application No. 61/244,323,filed Sep. 21, 2009, all of which are herein incorporated by referencein their entireties.

FIELD OF THE DISCLOSURE

Embodiments of the invention relate generally to narrow-band imaging,and, in particular, to methods and apparatus for defining wide-bandimage data based on narrow-band image data.

BACKGROUND OF THE DISCLOSURE

An image detector can be configured to receive and convert lightreflected from an object, after being emitted from a light source, intoone or more color channel signals. The color channel signal(s) can beused to define image data that can then be used to produce one or moreimages of the object on a display. For example, a full-color image ofthe object can be produced when the object is illuminated by a whitelight source. Many consumer products, such as video cameras and digitalcameras, have imaging systems with this capability.

If a narrow-band light source is used to illuminate an object, anarrowband image can be produced. This can be referred to as narrow-bandimaging. A narrow-band light source is a light source associated with anarrow spectrum of electromagnetic radiation compared to a spectrum ofelectromagnetic radiation associated with a wide-band light source.Imaging using a wide-band light source can be referred to as wide-bandimaging. In some applications, a narrow-band light source can be used toilluminate an object so that a narrow-band image that enhances specificfeatures of the object can be produced. For example, a red color lightsource can be used with an endoscopic system to help medicalpractitioners readily identify certain tissue structures that areenhanced when illuminated by the red color light.

In some applications, both narrow-band imaging and wide-band imaging aredesired. Because known imaging system do not produce images associatedwith a spectrum of light that is broader than the spectrum of lightemitted by the light source, often two different light sources are usedin these systems-a narrow-band light source and a wide-band lightsource. For example, known image processing systems are not capable ofproducing full-color images when the only light source included in thesystem is a red color light source. Thus, a need exists for methods andapparatus for defining wide-band image data based on narrow-band imagedata especially in applications where using a narrow-band light sourceis desirable.

SUMMARY OF THE DISCLOSURE

One exemplary aspect of the present disclosure is directed to an imagingmethod. The method may include receiving an intensity value of a firstspectral channel associated with a pixel location, wherein the intensityvalue of the first spectral channel is based on electromagneticradiation reflected from an object after being emitted from anarrow-band electromagnetic radiation source. The method may alsoinclude defining an intensity value of a second spectral channel basedon the intensity value of the first spectral channel, wherein the secondspectral channel is associated with a spectral region of electromagneticradiation different from a spectral region of electromagnetic radiationassociated with the first spectral channel. The method may furtherinclude associating the intensity value of the second spectral channelwith the pixel location.

Various embodiments of the disclosure may include one or more of thefollowing aspects: calculating the intensity value of the first spectralchannel based on a demosaic algorithm; the spectral region ofelectromagnetic radiation associated with the first spectral channel maybe separate from the spectral region of electromagnetic radiationassociated with the second spectral channel; the pixel location may beassociated with a pixel, wherein a spectral region of electromagneticradiation associated with the pixel may be modified in response toassociating the intensity value of the second spectral channel with thepixel location; receiving an intensity value of a third spectral channelassociated with the pixel location, wherein the third spectral channelmay be associated with a spectral region of electromagnetic radiationdifferent from the spectral region of electromagnetic radiationassociated with the second spectral channel, wherein defining theintensity value of the second spectral channel may be based on theintensity value of the third spectral channel; defining the intensityvalue of the second spectral channel may be based on a linearmathematical relationship; defining the intensity value of the secondspectral channel may be based on a coefficient associated with the firstspectral channel and a coefficient associated with the second spectralchannel; defining a first pixel of a first image based on the intensityvalue of the first spectral channel and the intensity value of thesecond spectral channel, wherein the first pixel may be associated withthe pixel location; and defining a second pixel of a second image basedon the intensity value of the first spectral channel and not based onthe intensity value of the second spectral channel, wherein the secondpixel may be associated with the pixel location.

Another exemplary aspect of the present disclosure is directed toanother imaging method. The method may include receiving a plurality ofsignals based on electromagnetic radiation reflected from an objectafter being emitted from a first electromagnetic source configured toemit electromagnetic radiation having a first spectral region ofelectromagnetic radiation. At least a portion of an image of the objectmay be based on the plurality of signals, the portion of the image beingassociated with a second spectral region of electromagnetic radiationbroader than the first spectral region of electromagnetic radiation.

Various embodiments of the disclosure may include one or more of thefollowing aspects: the second spectral region of electromagneticradiation may include at least a portion of the first spectral region ofelectromagnetic radiation; the image may be a red-green-blue (RGB)image, the first spectral region may be a narrow-band spectral region,and the second spectral region may be a red-green-blue (RGB) spectralregion; the electromagnetic radiation may be reflected at a first time,and the plurality of signals may be a first plurality of signals;receiving a second plurality of signals based on electromagneticradiation reflected at a second time from the object after being emittedfrom a second electromagnetic radiation source having a third spectralregion of electromagnetic radiation, wherein the third spectral regionof electromagnetic radiation may be different than the first spectralregion of electromagnetic radiation; defining the at least a portion ofthe image of the object may be based on the second plurality of signals;the second spectral region of electromagnetic radiation may include atleast a portion of the first spectral region of electromagneticradiation and at least a portion of the third spectral region ofelectromagnetic radiation; and defining the at least a portion of theimage of the object may be based on a back projection transform matrix.

Yet another exemplary aspect of the present disclosure is directed to acomputer-readable medium storing a set of instructions for executing aprocess. The process may include receiving a signal based onelectromagnetic radiation emitted from a narrow-band electromagneticradiation source, calculating a portion of a first pixel based on thesignal, and calculating a portion of a second pixel based on the portionof the first pixel and based on a correlation between narrow-bandresponsiveness data and wide-band responsiveness data.

Various embodiments of the disclosure may include one or more of thefollowing aspects: the portion of the first pixel may be associated withan intensity level of a first spectral channel, and the portion of thesecond pixel may be associated with an intensity level of a secondspectral channel, wherein the intensity level of the first spectralchannel may be different than the intensity level of the second spectralchannel; triggering emission of electromagnetic radiation at a specifiedintensity level from the narrow-band electromagnetic radiation source;and triggering a display of a portion of a first image based on thefirst pixel during a time period and triggering a display of a portionof a second image based on the second pixel during the time period.

In this respect, before explaining at least one embodiment of thepresent disclosure in detail, it is to be understood that the presentdisclosure is not limited in its application to the details ofconstruction and to the arrangements of the components set forth in thefollowing description or illustrated in the drawings. The presentdisclosure is capable of embodiments in addition to those described andof being practiced and carried out in various ways. Also, it is to beunderstood that the phraseology and terminology employed herein, as wellas the abstract, are for the purpose of description and should not beregarded as limiting.

The accompanying drawings illustrate certain exemplary embodiments ofthe present disclosure, and together with the description, serve toexplain the principles of the present disclosure.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be used as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present disclosure. It is important, therefore,to recognize that the claims should be regarded as including suchequivalent constructions insofar as they do not depart from the spiritand scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram that illustrates a signal processingmodule configured to define wide-band image data based on narrow-bandimage data, according to an embodiment of the invention;

FIG. 2 is a schematic graph of an electromagnetic radiation spectrumthat illustrates relative spectral regions of electromagnetic radiationassociated with FIG. 1, according to an embodiment of the invention;

FIG. 3A is a schematic graph that illustrates an electromagneticradiation emission from a narrow-band electromagnetic radiation source,according to an embodiment of the invention;

FIG. 3B is a schematic graph that illustrates a response of a pixelsensor to electromagnetic radiation reflected from an object after beingemitted from the narrow-band electromagnetic radiation source describedin connection with FIG. 3A, according to an embodiment of the invention;

FIG. 3C is a schematic graph that illustrates a set of signal valuescalculated based on the response of the pixel sensor shown in FIG. 3B,according to an embodiment of the invention;

FIG. 4 is a schematic diagram that illustrates a matrix of pixel sensorsthat collectively can be referred to as an electromagnetic radiationsensor, according to an embodiment of the invention;

FIG. 5 illustrates narrow-band responsiveness data and wide-bandresponsiveness data that can be used to define a correlation, accordingto an embodiment of the invention;

FIG. 6 is a flowchart that illustrates a calibration method, accordingto an embodiment of the invention;

FIG. 7 is a flowchart that illustrates a method for calculating anintensity value associated with a spectral channel based on an intensityvalue associated with a different spectral channel, according to anembodiment of the invention;

FIG. 8A is a schematic graph that illustrates an electromagneticradiation emission from a first narrow-band electromagnetic radiationsource, according to an embodiment of the invention;

FIG. 8B is a schematic graph that illustrates a response of a pixelsensor to the electromagnetic radiation emission shown in FIG. 8A,according to an embodiment of the invention;

FIG. 8C is a schematic graph that illustrates an electromagneticradiation emission from a second narrow-band electromagnetic radiationsource that occurs after the electromagnetic radiation emission shown inFIG. 8A, according to an embodiment of the invention;

FIG. 8D is a schematic graph that illustrates a response of a pixelsensor to the electromagnetic radiation emission shown in FIG. 8C,according to an embodiment of the invention; and

FIG. 8E is a schematic graph that illustrates intensity valuescalculated based on the pixel responses shown in FIGS. 8B and 8D,according to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic block diagram that illustrates a signal processingmodule 130 configured to define wide-band image (WBI) data 170 based onnarrow-band image (NBI) data 160, according to an embodiment of theinvention. The narrow-band image data 160 is defined by the signalprocessing module 130 based on a signal from a sensor 120 that isconfigured to receive electromagnetic (EM) radiation emitted 42 from anarrow-band electromagnetic radiation source 110 and reflected 44 (e.g.,scattered) from an object 140 (e.g., a target, a target object). Thenarrow-band electromagnetic radiation source 110 can also be referred toas a narrowband electromagnetic light source. Electromagnetic radiationincludes, for example, radio waves, microwaves, terahertz radiation,infrared radiation, visible light, ultraviolet radiation, x-rays, gammarays, and so forth.

The wide-band image data 170 is associated with a spectral region ofelectromagnetic radiation that is broader than a spectral region ofelectromagnetic radiation that is associated with the narrow-band imagedata 160. In other words, at least a portion of the spectral region ofelectromagnetic radiation associated with the wide-band image data 170falls outside of the spectral region of electromagnetic radiationassociated with the narrow-band image data 160. In some embodiments, atleast a portion of the wide-band image data 170 is associated withwavelengths of electromagnetic radiation that fall outside of thespectral region of electromagnetic radiation associated with thenarrow-band image data 160. The portion of the spectral region ofelectromagnetic radiation that falls outside of the spectral regionassociated with the narrow-band image data 160 can be calculated basedon, for example, a mathematical relationship.

In this embodiment, the signal processing module 130 is a componentwithin an imaging system 100 that also includes the narrow-bandelectromagnetic radiation source 110 and the sensor 120. The signalprocessing module 130 can be a hardware-based module (e.g., a digitalsignal processor (DSP), a field programmable gate array (FPGA)) and/or asoftware-based module (e.g., a module of computer code, a set ofprocessor-readable instructions that can be executed at a processor). Insome embodiments, the signal processing module 130 can include and/orcan be associated with a memory (not shown in FIG. 1) and/or a processor(not shown in FIG. 1). The narrow-band electromagnetic radiation source110 can be any type of electromagnetic radiation source configured toemit electromagnetic radiation. For example, the narrow-bandelectromagnetic radiation source 110 can be a light emitting diode(LED), a tungsten-based emitter, an infrared source, and so forth.

The sensor 120 can be any type of sensor that can be used to receiveelectromagnetic radiation, and in response, define a signal such as, forexample, an analog signal (e.g., a voltage-based signal, afrequency-based signal) or a digital signal. The sensor 120 can be acollection of individual sensors that can be referred to as a pixel oras pixel sensors. The sensor 120 can include a filter (not shown)configured to separate different spectral regions of electromagneticradiation that can be associated with a spectral channel and one or morephoto-detecting elements (not shown). The photo-detecting elements canbe part of, for example, a charge-coupled device (CCD) and/or acomplementary metal-oxide-semiconductor (CMOS) device. The filter canbe, for example, a Bayer filter, a red-green-blue-cyan (RGBC) filter, acyan-yellow-magenta-green (CYMG) filter, and/or a dichroic prism filter.In some embodiments, the sensor 120 can be a Foveon X3 sensor, a thermalimaging sensor, a video camera tube, a gamma camera sensor, an x-raysensor, etc. In some embodiments, the sensor 120 can be used with, forexample, a lens or set of lenses (not shown); which may compriseadditional filtering elements.

A spectral channel can be associated with a band of wavelengths and canbe centered around, for example, a color such as a primary color (e.g.,red, blue, green). In some embodiments, when a spectral channel iscentered around a wavelength (e.g., a wavelength measured in nm) thatcorresponds with a substantially uniform color (e.g., a green color),the spectral channel can be referred to as a color channel. Differentspectral regions of electromagnetic radiation can be associated with oneor more signals that can each be produced by, for example, differentCCDs within sensor 120 or multiple sensors (not shown).

The narrow-band image data 160 can be used to define a narrow-band imageof the object 140 (not shown in FIG. 1) and the wide-band image data 170can be used to define a wide-band image of the object 140 (not shown inFIG. 1). Image data can include, for example, any information that canbe used to produce an image. The image data can include information suchas, for example, a raw signal defined by a portion of the sensor 120(e.g., an individual pixel sensor), a pixel location value associatedwith a portion of the sensor 120, a pixel location value associated witha display (not shown in FIG. 1), a saturation value, a luma value, achroma value, and/or an intensity value (e.g., an intensity valueexpressed as a digital number (DN), expressed in lumens (1 m) or candela(cd) per square foot (ft²)) associated with a spectral region ofelectromagnetic radiation (e.g., a spectral channel). The narrow-bandimage data 160 and/or the wide-band image data 170 can be defined aftera demosaic algorithm (e.g., a demosaic color interpolation) and/or acompression algorithm has been executed.

In some embodiments, a narrow-band image and/or a wide-band image can bedisplayed on one or more displays (not shown in FIG. 1) such as a liquidcrystal display (LCD). The image based on the narrow-band image data 160can be used to define features that may be difficult for a personviewing the image to distinguish in a wide-band image (e.g., tissuestructures in an image of a patient's internal organs, blood vesselswithin a tissue). In some embodiments, one or more images based on thenarrow-band image data 160 and/or one or more images based on thewide-band image data 170 can be displayed on one or more displayssimultaneously. For example, a narrow-band image and a wide-band imagecan be overlaid on a single display after pseudo-color post-processing.The simultaneous display of the narrow-band image and the wide-bandimage can be used by a person viewing the images to distinguish featuresand/or understand portions that would be difficult to discern withoutthe simultaneous display. In some embodiments, the wide-band image data160 and/or the narrow-band image data 170 can be used to produce atleast a portion of a video.

In some embodiments, the narrow-band image data 160 can be characterizedas narrow-band because the spectral region of electromagnetic radiationassociated with the narrow-band image data 160 is based on a spectralregion of electromagnetic radiation emitted from the narrow-bandelectromagnetic radiation source 110. In some embodiments, thenarrow-band electromagnetic radiation source 110 can be a radiationsource that emits a spectral region of electromagnetic radiation that issubstantially less than a spectral region of electromagnetic radiationemitted from a white light source. For example, the narrow-bandelectromagnetic radiation source 110 can be configured to emit a narrowspectral region centered around a specified wavelength such as 530nanometers (nm) or centered around a specified color such as red (e.g.,between 630 nm and 700 nm). In some embodiments, the wide-band imagedata 160 can be used to produce a full-color image (e.g., red-green-blue(RGB) image) associated with a spectral region of electromagneticradiation substantially corresponding to a white light source. In someembodiments, the terms narrow-band and wide-band are used to distinguishrelative ranges of spectral regions.

FIG. 2 is a schematic graph of an electromagnetic radiation spectrumthat illustrates relative spectral regions of electromagnetic radiationassociated with FIG. 1, according to an embodiment of the invention. Thenarrow-band electromagnetic radiation source 110 can be configured toemit electromagnetic radiation 42 (as shown in FIG. 1) with an intensityprofile 210 that has a spectral region X centered about wavelength Y asshown in FIG. 2. Accordingly, the electromagnetic radiation reflected 44from the object 140 and transmitted as a signal from the sensor 120 tothe signal processing module 130 (as shown in FIG. 1) will have aspectral region substantially equal to spectral region X as shown inFIG. 2. Furthermore, the narrowband image data 160 will be associatedwith (e.g., based on) a spectral region of electromagnetic radiationthat is substantially equal to spectral region X because the narrow-bandimage 160 will be defined based on the signal from the sensor 120.

The wide-band image data 170 is associated with (e.g., based on)electromagnetic radiation that has a spectral region Z. As shown in FIG.2, in some embodiments, the spectral region Z can correspond with aspectral region of electromagnetic radiation from a wide-bandelectromagnetic source (e.g., wide-band light source) that has anintensity profile 220. In some embodiments, the spectral region X can becentered around a wavelength Y that corresponds with the color red andthe spectral region Z can correspond with a spectral region ofelectromagnetic radiation from a white light source.

Referring back to FIG. 1, the wide-band image data 170 can be defined bythe signal processing module 130 based on a correlation betweennarrow-band responsiveness data and wide-band responsiveness data. Thenarrow-band responsiveness data can be based on two or more signalsdefined by the sensor 120 (e.g., an archetypical sensor) in response toelectromagnetic radiation emitted from the narrow-band electromagneticradiation source 110. In other words, the narrow-band responsivenessdata can be representative of a responsiveness of the sensor 120 toelectromagnetic radiation emitted from the narrow-band electromagneticradiation source 110. The wide-band responsiveness data can represent asignal defined by sensor 120 (e.g., an archetypical sensor) in responseto electromagnetic radiation emitted from a wide-band electromagneticradiation source (not shown in FIG. 1). In other words, the wide-bandresponsiveness data can be representative of a responsiveness of thesensor 120 to electromagnetic radiation emitted from the widebandelectromagnetic radiation source. More details related to wide-bandresponsiveness data and narrow-band responsiveness data are discussed inconnection with FIG. 5.

In some embodiments, the correlation between the narrow-bandresponsiveness data and the wide-band responsiveness data can beexpressed as a mathematical relationship. The mathematical relationshipcan be a function of narrow-band image data 160, can be accessed by thesignal processing module 130, and can be used to the calculate thewide-band image data 170. More details related to the nature of thecorrelation (e.g., the mathematical relationship) will be discussed inconnection with FIG. 3.

In some embodiments, the imaging system 100 can be used in a medicaldevice such as an endoscope or a tool that has an imaging capability. Insome embodiments, the narrow-band electromagnetic radiation source 110and/or the sensor 120 can be disposed in a separate housing from thesignal processing module 130.

FIG. 3A is a schematic graph that illustrates an electromagneticradiation emission from a narrow-band electromagnetic radiation source,according to an embodiment of the invention. The narrow-bandelectromagnetic radiation source can be a narrow-band electromagneticradiation source such as that shown in FIG. 1. The narrow-bandelectromagnetic radiation source can be configured to emit a spectralregion 310 of electromagnetic radiation centered around a wavelength Rat an intensity value of P. In this embodiment, the wavelength Rcorresponds with a red color in a visible electromagnetic spectrum.Because the narrow-band electromagnetic radiation source is configuredto emit electromagnetic radiation centered around a wavelength thatcorresponds with a red color, the narrow-band electromagnetic radiationsource can be referred to as a red-color-channel electromagneticradiation source.

FIG. 3B is a schematic graph that illustrates a response of a pixelsensor to electromagnetic radiation reflected from an object after beingemitted from the narrow-band electromagnetic radiation source describedin connection with FIG. 3A, according to an embodiment of the invention.The pixel sensor can be a pixel sensor from a sensor such as that shownin FIG. 1 (e.g., sensor 120). As shown in FIG. 3B, the pixel sensor ofthe electromagnetic radiation sensor produces a signal 306 at a signalvalue of Q at wavelength R (e.g., at the red wavelength). The signalvalue can be, for example, an analog value (e.g., a voltage-basedsignal, a frequency-based signal), or a digital value (e.g., digitalnumber (DN)). In some embodiments, the signal value can be or can becorrelated with, for example, an intensity value.

In the embodiment shown in FIG. 3B, the pixel sensor is configured todetect electromagnetic radiation centered around wavelength R andproduce the signal 306 in response. In other words, the pixel sensor isconfigured to respond to (e.g., have a significant response to)electromagnetic radiation associated with color channel R (also can bereferred tows spectral channel R). Accordingly, the pixel sensor can bereferred to as an R color channel pixel sensor. Because the wavelength Rcorresponds to a wavelength that has a red color, the pixel sensor canalso be referred to as a red-color-channel pixel sensor.

In some embodiments, the electromagnetic radiation sensor can have pixelsensors configured to respond to electromagnetic radiation associatedwith additional color channels such as a green color channel. The pixelsensors that are not configured to respond to the electromagneticradiation emitted from the narrow-band electromagnetic radiation source,however, will not be able to produce a signal.

Any parameter values associated with signal 306 (e.g., the signal value)can be associated with a pixel location value. In some embodiments, thepixel location value can be based on an x/y coordinate system or can bea unique alphanumeric value associated with the pixel sensor. Forexample, the pixel sensor can be an individual sensor from a matrix ofpixel sensors such as pixel sensor 444 shown in FIG. 4.

FIG. 4 is a schematic diagram that illustrates a matrix of pixel sensorsthat collectively can be referred to as an electromagnetic radiationsensor 440, according to an embodiment of the invention. As shown inFIG. 4, pixel sensor 444 is associated with pixel location value (c, 4).In some embodiments, the electromagnetic radiation sensor 440 can haveone or more pixel sensors configured to respond to electromagneticradiation associated with different spectral channels. For example, theelectromagnetic radiation sensor can include or be coupled to a Bayerfilter with a filter pattern that includes 50% green-color-channel pixelsensors, 25% red-color-channel pixel sensors, and 25% blue-color-channelpixel sensors.

Referring back to FIG. 3B, if the pixel sensor includes or is coupled toa filter (e.g., a Bayer filter) that has groups of pixel sensorsconfigured to variously respond to electromagnetic radiation associatedwith different spectral channels, a new signal (not shown) calculatedbased on signal 306 of the pixel sensor can be associated with a pixellocation value after a demosaic calculation has been performed. Forexample, the new signal can be a signal calculated based on a demosaicalgorithm and can be associated with a pixel location value definedbased on the demosaic algorithm. In some embodiments, the pixel locationvalue can be defined based on and/or can be associated with a locationassociated with an image or a location associated with a display.

A collection of narrow-band signal values (e.g., a collection of valuesbased on signals such as signal 306 shown in FIG. 3B) can be used toproduce a narrow-band image. Because signal 306 is a response from anemission from the narrow-band electromagnetic radiation source (shown inFIG. 3A), a full-color image cannot be produced without definingadditional signal information (e.g., green signal information and/orblue signal information when red signal information is collected) basedon, for example, a mathematical relationship.

FIG. 3C is a schematic graph that illustrates a set of signal valuescalculated based on the response of the pixel sensor shown in FIG. 3B,according to an embodiment of the invention. The set of signals isassociated with a spectral region of electromagnetic radiation includespectral region outside of spectral region 310 shown in FIG. 3A.Specifically, the response of the red-color-channel pixel sensor fromFIG. 3B is used to define a set of signal values that includes a signalvalue associated with a red color channel, a signal value associatedwith a green color channel, and a signal value associated with a bluecolor channel. The wavelengths B and G shown in FIG. 3B correspond,respectively, with a wavelength of a blue color and a wavelength of agreen color.

Signal 302 with a signal value of S at wavelength B, and signal 304 witha signal value of R at wavelength G are calculated based on the signalvalue of Q associated with signal 306 (also shown in FIG. 3B) atwavelength R. Signal 302 and signal 304 are, respectively, associatedwith wavelengths G and B, which fall outside of the spectral region 310associated with the narrow-band electromagnetic radiation source (shownin FIG. 3A).

In this embodiment, because the signal values 302, 304, and 306 are eachassociated with a color from a full-color space, the signals 302, 304,and 306 can be used to produce a pixel associated with a full-colorimage. In some embodiments, signals 302 and 304 can each be associatedwith a spectral channel that overlaps with at least a portion of thespectral region 310 associated with the narrow-band electromagneticradiation source (shown in FIG. 3A).

The signals 302 and 304 can be calculated based on a mathematicalrelationship defined based on a correlation between narrow-bandresponsiveness data associated with wavelength R and wide-bandresponsiveness data associated with the set of full-color wavelengths R,G, and B. Specifically, one or more portions of the mathematicalrelationship can be defined based on the narrow-band responsiveness dataand the wide-band responsiveness data. Defining the mathematicalrelationship can include, for example, defining the form of themathematical relationship, defining parameters/variables within themathematical relationship, and/or coefficients within the mathematicalrelationship. After the mathematical relationship has been defined, themathematical relationship can be used at one or more signal processingmodules of an imaging system such as that shown in FIG. 1. More detailsrelated to a method for defining a mathematical relationship aredescribed in connection with FIG. 6.

For example, a set of signal values (such as that described inconnection with FIG. 3C) for a full-color pixel included in a wide-bandvector WB_(mn) and associated with a pixel location value specified byrow m and column n can be calculated using the mathematical relationshipWB_(mn) =NB_(mn) ·T, which is expressed in general terms and whereNB_(mn) can be a narrow-band vector. In this mathematical relationshipNB_(mn) =(NB_(mn) ^(R)), WB_(mn) =(WB_(mn) ^(R), WB_(mn) ^(G), WB_(mn)^(B)), and T is a 3×3 linear matrix of coefficients

$T = {\begin{matrix}t_{r}^{R} & t_{r}^{G} & t_{r}^{B} \\t_{g}^{R} & t_{g}^{G} & t_{g}^{B} \\t_{b}^{R} & t_{b}^{G} & t_{b}^{B}\end{matrix}.}$The signal value NB_(mn) ^(R) is also associated with pixel locationvalue (m, n) and is defined in response to electromagnetic radiationemitted from a narrow-band electromagnetic radiation source associatedwith a red color channel (similar to that shown in FIG. 3A). The signalvalues WB_(mn) ^(R), WB_(mn) ^(G), WB_(mn) ^(B) are associated with thered color channel, a green color channel, and a blue color channel,respectively. A signal value for an individual color channel, such asthe red color channel WB_(mn) ^(R), can thus be calculated as WB_(mn)^(R)=NB_(mn) ^(R)·t_(r) ^(R), which is an equation derived from themathematical relationship WB_(mn) =NB_(mn) ·T. The red color channelWB_(mn) ^(R) is calculated based on the signal value NB_(mn) ^(R) andcoefficient t_(r) ^(R) from matrix T. A signal value for the green colorchannel WB_(mn) ^(G) can be calculated in a like manner based on NB_(mn)^(R).

The coefficients within matrix T can be defined so that when NB_(mn) isdefined based on electromagnetic radiation reflected from an objectafter being emitted from a narrow-band electromagnetic radiation source,a set of signal values included in vector WB_(mn) can be calculated. IfT is the identity matrix, WB_(mn) will be equal to NB_(mn) .

In some embodiments, the matrix T (e.g., one or more of the coefficientsof the matrix T) can be defined using a Finlayson Maximum Ignorance withPositivity (MIP) method. Details related to the Finlayson MIP method aredescribed in Finlayson et al., “The Maximum Ignorance Assumption withPositivity,” Final Program and Proceedings of the IS&T/SID Fourth ColorImaging Conference, pp. 202-205 (1996), which is incorporated herein byreference in its entirety. In some embodiments, the coefficients withinmatrix T can be defined by, for example, minimizing the least-squareserror between any combination of variables and values included innarrow-band responsiveness data and wide-band responsiveness data. Anexample of wide-band responsiveness data and narrow-band responsivenessdata is shown in FIG. 5.

In some embodiments, the mathematical relationship can be modified forany number of spectral channels. For example, the vector NB_(mn) can bedefined to include signal values associated with two color channelswithin a narrow spectrum of electromagnetic radiation and the vectorWB_(mn) can be defined to include signal values associated with threecolor channels over a spectral region of electromagnetic radiationbroader than the narrow spectrum. In some embodiments, the matrix T canbe referred to as a back projection transform matrix.

FIG. 5 illustrates narrow-band responsiveness data 500 and wide-bandresponsiveness data 580 that can be used to define a correlation,according to an embodiment of the invention. The narrow-band responsivedata 500 includes a set of first spectral channel response values 560defined in response to electromagnetic radiation reflected from a targetafter being emitted from a narrow-band electromagnetic radiation source.For example, at narrow-band intensity value NB₁ (column 550), the firstspectral channel response value is NI^(First) ₁ (column 560).

The wide-band responsive data 580 includes a first Spectral channelresponse value 520, a second spectral channel response value 530, and athird spectral channel response value 540. Each of the spectral channelresponse values 520, 530, and 540 are response values defined inresponse to electromagnetic radiation reflected from the target afterbeing emitted from a wide-band electromagnetic radiation source atwide-band intensity values 510. For example, at wide-band intensityvalue WB₁ (column 510), the first spectral channel response value isWI^(First) ₁ (column 520).

In some embodiments, the narrow-band responsiveness data 500 and thewide-band responsiveness data 580 can be produced by illuminating one ormore targets (e.g., one or more images) from a target database using thenarrow-band electromagnetic radiation source and the wide-bandelectromagnetic radiation source, respectively. In some embodiments, thenarrow-band responsiveness data 500 and the wide-band responsivenessdata 580 can be produced using archetypical electromagnetic radiationsources. For example, the narrow-band responsiveness data 500 and thewide-band responsiveness data 580 can be produced using anelectromagnetic radiation source that is similar to those that would beused in an actual application. In some embodiments, the narrow-bandresponsiveness data 500 and the wide-band responsiveness data 580 can beproduced under a variety of specified conditions (e.g., a specifiedtemperature).

In some embodiments, the narrow-band responsiveness data 500 and thewide-band responsiveness data 580 can be used to produce a correlationexpressed as a look-up table. In some embodiments, the narrow-bandresponsiveness data 500 and the wide-band responsiveness data 580 can beassociated with a particular region of a sensor. Narrow-bandresponsiveness data 500 and/or wide-band responsiveness data 580associated with the particular region can be referred to asregion-specific data. Accordingly, a correlation produced based on theregion-specific data can be used to calculate wide-band image dataassociated with the particular region of the sensor based on narrow-bandimage data associated at the particular region of the sensor.

FIG. 6 is a flowchart that illustrates a calibration method, accordingto an embodiment of the invention. As shown in the flowchart,narrow-band responsiveness data and wide-band responsiveness data arereceived at 600. In some embodiments, the narrow-band responsivenessdata and the wide-band responsiveness data can be similar to that shownin FIG. 5.

A mathematical relationship (also can be referred to as a calibratedrelationship) is defined based on the narrow-band responsiveness dataand the wide-band responsiveness data at 610. Defining the mathematicalrelationship can include, for example, defining the form of themathematical relationship, defining parameters/variables within themathematical relationship, and/or coefficients within the mathematicalrelationship.

At least a portion of the mathematical relationship is uploaded to animaging system at 620. In some embodiments, the mathematicalrelationship and/or portions of the mathematical relationship (e.g.,only coefficients) can be uploaded to one or more imaging systems. Insome embodiments, the mathematical relationship can be defined within aset of instructions (e.g., a computer program, a computer application)uploaded to an imaging system. In some embodiments, a library ofmathematical relationships, parameters/variables, and/or coefficientsassociated with one or more narrow-band electromagnetic radiationsources and/or wide-band electromagnetic radiation sources can beuploaded to an imaging system.

A first signal value is defined at the imaging system based onelectromagnetic radiation emitted from a narrow-band electromagneticradiation source and reflected from an object at 630. In someembodiments, the first signal value can be, for example, an intensityvalue.

A second signal value is calculated based on the first signal value andbased on the mathematical relationship at 640. The second signal valuecan be associated with a wide-band electromagnetic radiation spectrum(e.g., an electromagnetic radiation spectrum associated with a wide-bandlight source). In some embodiments, the mathematical relationship can beselected from a library of mathematical relationships based on thenarrow-band electromagnetic radiation source.

FIG. 7 is a flowchart that illustrates a method for calculating anintensity value associated with a spectral channel based on an intensityvalue associated with a different spectral channel, according to anembodiment of the invention. As shown in the flowchart, electromagneticradiation is emitted from a narrow-band electromagnetic radiation sourcetoward an object at 700. The electromagnetic radiation can besubstantially centered around a particular wavelength of electromagneticradiation associated with a specified visible color. In someembodiments, the narrow-band electromagnetic radiation source can emit aregion of electromagnetic radiation that is associated with a spectralchannel (e.g., red color channel).

Electromagnetic radiation reflected from the object is received at animage detector at 710. The image detector can include, for example, oneor more lenses, processing elements, and/or a sensor such as a CCDsensor or sensor with a Bayer filter.

An intensity value associated with a first spectral channel is definedbased on the reflected electromagnetic radiation at 720. The intensityvalue can be defined based on, for example, a voltage signal from theimage detector. The first spectral channel can be associated with aregion of electromagnetic radiation that substantially corresponds witha region of electromagnetic radiation associated with the narrow-bandelectromagnetic radiation source.

The intensity value associated with the first spectral channel isreceived and associated with a pixel location value at 730. The pixellocation value can be associated with a pixel sensor from a CCD sensor,a location (e.g., a pixel) associated with an image, and/or a location(e.g., a pixel) associated with a display. In some embodiments, theintensity value can be associated with the pixel location value (block730) simultaneous to the intensity value being defined (block 720).

An intensity value associated with a second spectral channel is definedbased on the intensity value of the first spectral channel at 740 and acorrelation between narrow-band responsiveness data and wide-bandresponsiveness data. The narrow-band responsiveness data can beassociated with a responsiveness of a sensor to a electromagneticradiation from a narrow-band electromagnetic source (e.g., a red LED).The wide-band responsiveness data can be associated with aresponsiveness of a sensor to a electromagnetic radiation from awide-band electromagnetic source (e.g., a white light source).

The second spectral channel can be associated with a region ofelectromagnetic radiation different than a region of electromagneticradiation associated with the narrow-band electromagnetic radiationsource and/or the first spectral channel. In some embodiments, the firstspectral channel and the second spectral channel can be associated withregions of electromagnetic radiation that at least partially overlap.The second spectral channel can be associated with a region ofelectromagnetic radiation that is within a region of electromagneticradiation emitted by the wide-band electromagnetic radiation source.

An intensity value of the second spectral channel is associated with thepixel location value at 750. The intensity value of the first spectralchannel and the intensity value of the second spectral channel can beassociated with the pixel location value within a database.

An image is defined based on the intensity value associated with thefirst spectral channel and/or based on the intensity value associatedwith the second spectral channel at 760. In some embodiments, theintensity value associated with the first spectral channel and theintensity value associated with the second spectral channel can be usedto define a pixel within an image. For example, if the first spectralchannel is a green color channel and the second spectral channel is ared color channel, the intensity value associated with the firstspectral channel and the intensity value associated with the secondspectral channel can be used to produce a pixel that has a color that isa mixture of green and red. In some embodiments, any combination of theintensity values can be used to produce multiple images simultaneously(e.g., multiple images displayed on multiple displays) or separately(e.g., multiple images displayed on a single display).

In some embodiments, if the intensity value associated with the firstspectral channel and the intensity value associated with the secondspectral channel are associated with a first color space (e.g., an RGBcolor space), the intensity values can be combined and/or translatedinto a different color space (e.g., a hue-saturation-brightness (HSB)color space, a hue-saturation-lightness (HSL) color space). Althoughthis embodiment is related to the calculation of intensity values, theflowchart can be applied to the calculation of any type of image data(e.g., a raw signal value from a sensor).

FIGS. 8A through 8E are schematic graphs that illustrate intensityvalues calculated based on responses from two different narrow-bandelectromagnetic emissions at different times, according to an embodimentof the invention. The x-axis of all of the graphs is wavelength, and they-axis of all of the graphs is intensity value.

FIG. 8A is a schematic graph that illustrates an electromagneticradiation emission from a first narrow-band electromagnetic radiationsource, according to an embodiment of the invention. As shown in FIG.8A, the electromagnetic radiation emission is substantially centeredaround a wavelength Y.

FIG. 8B is a schematic graph that illustrates a response of a pixelsensor to the electromagnetic radiation emission shown in FIG. 8A,according to an embodiment of the invention. In this embodiment, theresponse is shown as a point 802 that has an intensity value atwavelength Y. In some embodiments, the pixel sensor can be configured toonly produce a signal in response to electromagnetic radiation emittedat wavelength Y.

FIG. 8C is a schematic graph that illustrates an electromagneticradiation emission from a second narrow-band electromagnetic radiationsource that occurs after the electromagnetic radiation emission shown inFIG. 8A, according to an embodiment of the invention. As shown in FIG.8C, the electromagnetic radiation emissions is substantially centeredaround a wavelength Z.

FIG. 8D is a schematic graph that illustrates a response of a pixelsensor to the electromagnetic radiation emission shown in FIG. 8C,according to an embodiment of the invention. In this embodiment, theresponse is shown as a point 804 that has an intensity value atwavelength Z. In some embodiments, the pixel sensor can be configured toproduce a signal only in response to electromagnetic radiation emittedat wavelength Z. Even though the responses shown in FIGS. 8B and 8D,respectively, can be defined based on signals from different pixelsensors, the responses can be associated with a single pixel locationvalue.

FIG. 8E is a schematic graph that illustrates intensity valuescalculated based on the pixel responses shown in FIGS. 8B and 8D,according to an embodiment of the invention. Specifically, point 810 atwavelength X and point 820 at wavelength W are calculated based on theintensity values associated with points 802 and 804. The points 810 and820 can be associated with the same pixel location value with whichpoints 820 and 804 are associated. The intensity values associated withpoints 802, 804, 810, and 820 can be used to calculate a pixel valuethat can be used to produce an image that has a portion corresponding tothe pixel location value. In some embodiments, any combination of theintensity values associated with points 802, 804, 810, and 820 can beused to produce multiple images simultaneously or in succession.

The wavelengths Y and Z fall within a narrow-band spectral region 830and the wavelengths W, X, Y, and Z fall within a wide-band spectralregion 840. Moreover, the wavelengths Wand X fall outside of thenarrow-band spectral region 830. The points 810 and 820 are calculatedbased on a correlation between narrowband responsiveness data andwide-band responsiveness data. In some embodiments, the narrow-bandresponsiveness data can be based on data associated with wavelengthsincluded in the narrow-band spectral region 830 and the wide-bandresponsiveness data based on data associated with wavelengths includedin the wide-band spectral region 840.

Some embodiments of the invention relate to a computer storage productwith a computer-readable medium (also can be referred to as aprocessor-readable medium) having instructions or computer code thereonfor performing various computer-implemented operations. The media andcomputer code (also referred to as code) may be those specially designedand constructed for the specific purpose or purposes. Examples ofcomputer-readable media include, but are not limited to: magneticstorage media such as hard disks, floppy disks, and magnetic tape;optical storage media such as Compact Disc/Digital Video Discs(“CD/DVDs”), Compact Disc-Read Only Memories (“CD-ROMs”), andholographic devices; magneto-optical storage media such as flopticaldisks; carrier wave signals; and hardware devices that are speciallyconfigured to store and execute program code, such as ApplicationSpecific Integrated Circuits (“ASICs”), Programmable Logic Devices(“PLDs”), and Read-Only Memory (“ROM”) and Random-Access Memory (“RAM”)devices. Examples of computer code include, but are not limited to,micro-code or microinstructions, machine instructions, such as producedby a compiler, and files containing higher-level instructions that areexecuted by a computer using an interpreter. For example, an embodimentof the invention may be implemented using Java, C++, or otherobject-oriented programming language and development tools. Additionalexamples of computer code include, but are not limited to, controlsignals, encrypted code, and compressed code.

The many features and advantages of the present disclosure are apparentfrom the detailed specification, and thus, it is intended by theappended claims to cover all such features and advantages of the presentdisclosure which fall within the true spirit and scope of the presentdisclosure. Further, since numerous modifications and variations willreadily occur to those skilled in the art, it is not desired to limitthe present disclosure to the exact construction and operationillustrated and described, and accordingly, all suitable modificationsand equivalents may be resorted to, falling within the scope of thepresent disclosure.

What is claimed is:
 1. An imaging system, comprising: an electromagneticradiation source configured to emit a first electromagnetic radiationemission; a detector configured to receive a reflection of the firstelectromagnetic radiation emission from an object, the reflection of thefirst electromagnetic radiation emission from the object having a firstset of characteristics; and a processor operatively coupled to thedetector and configured to determine one or more of a second set ofcharacteristics, associated with a reflection of a secondelectromagnetic radiation emission from the object, based at least inpart on the first set of characteristics, wherein the reflection of thefirst electromagnetic radiation emission covers a narrower band of anelectromagnetic radiation spectrum than a band of the electromagneticspectrum covered by the reflection of the second electromagneticradiation emission, and wherein the processor determines one or more ofthe second set of characteristics in the absence of receipt of thereflection of the second electromagnetic radiation emission by thedetector.
 2. The imaging system of claim 1, wherein the electromagneticradiation source is a light source, and the light source is the solelight source of the imaging system.
 3. The imaging system of claim 1,wherein the first electromagnetic radiation emission is a lightemission, and the light emission is the sole light emission of theimaging system.
 4. The imaging system of claim 1, further including anendoscope, wherein at least the electromagnetic radiation source and thedetector are mounted on the endoscope.
 5. The imaging system of claim 1,wherein the first electromagnetic radiation emission is an emission oflight of a first color, and the second electromagnetic radiationemission includes an emission of light of a second color different fromthe first color.
 6. The imaging system of claim 1, wherein the detectorincludes a plurality of pixel sensors, and at least one pixel sensor ofthe plurality of pixel sensors is configured to generate a signal uponreceiving the reflection of the first electromagnetic radiationemission, the signal being received by the processor.
 7. An imagingsystem, comprising: a light source for emitting a first type of light; adetector for receiving a reflection of the first type of light off of anobject, and sending a signal indicative of a characteristic of thereflection of the first type of light off of the object; and aprocessor, operatively coupled to the detector, configured to determinea signal indicative of a characteristic of a reflection of a second typeof light off of the object, based at least in part on the signalindicative of the characteristic of the reflection of the first type oflight, wherein the reflection of the first type of light is from anarrower band of an electromagnetic radiation spectrum than a band ofthe electromagnetic spectrum covered by the second type of light, andwherein the processor determines the signal indicative of thecharacteristic of the reflection of the second type of light in theabsence of receipt of the reflection of the second type of light by thedetector.
 8. The imaging system of claim 7, wherein the light source isthe only light source in the imaging system.
 9. The imaging system ofclaim 7, wherein the first type of light is the only type of lightemitted by the imaging system.
 10. The imaging system of claim 7,further including an endoscope, wherein at least the light source andthe detector are mounted on the endoscope.
 11. The imaging system ofclaim 7, further including a display, operatively coupled to thedetector, for displaying an image based at least in part on the signalindicative of the characteristic of the second type of light.
 12. Theimaging system of claim 7, wherein the first type of light is light of afirst color, and the second type of light includes light of a secondcolor different from the first color.